Subscriber terminals, such as personal digital assistants and other types of portable computers using data radio transceivers are being used in a wide variety of applications. Such terminals may be used in a variety of circumstances such as requesting stock quotes, accessing data files or a central data processing center or immediate access to time sensitive information like E-mail messages. Examples of such subscriber terminals include various personal digital assistants (PDA) or palmtop computers developed by Motorola, Inc. Subscriber terminals such as these operate in conjunction with wireless telecommunications infrastructure equipment (i.e., the ARDIS infrastructure system operated by Motorola). The wireless infrastructure equipment typically includes stationary transceivers interconnected with a local telephone network or other data network or transfer facility.
Typically, upon receiving a request to transmit, a data transceiver transmits a request to send and then waits for authorization to send before transmitting or sending a data packet. In the case of receiving a data communications, a data transceiver ordinarily includes a call selective receiver for recognizing and receiving only calls directed to the target subscriber terminal.
As with any wireless system a signal directed to a subscriber terminal by way of a wireless data receiver may be blocked by a hill or other tall object that unduly attenuates the signal. Further, at some radio signal levels, noise generated within the computer portion of a subscriber terminal by clocking devices or switching power supplies may result in a signal to noise ratio of such a low level as to render the signal unintelligible. Past efforts directed to reducing internally generated noise sources have taught that shielding and physical isolation of significant noise sources from the receiver section are an effective means of improving the signal to noise ratio. Because of the importance and wide spread usage of subscriber terminals including portable computers and other portable digital systems a need exists for more effective techniques of suppressing the effects or desensitization of radio frequency receivers resulting from the noise generated within such devices.